This invention relates to braking apparatus and, more particularly, to braking apparatus for a web transport system, for example a web transport for a tape recording and/or playback device.
In a typical web transport system, such as in a tape transport system for use in a recording and/or playback device, the web is driven between rotary members by driving one of the rotary members from a suitable source, such as a motor. When web movement is to be arrested, the driving motor usually is deenergized. In many instances, the transmission between the motor and the driven rotary member is such that when the motor is deenergized, the rotary member effectively is braked. However, the non-driven rotary member tends to continue to rotate, or freewheel, unless positive braking forces are exerted thereon. Typically, such braking forces are exerted by brake shoes.
A modification of the aforedescribed web transport system is found in tape recording/playback devices. In such devices, a first motor generally drives a take-up reel and capstan during recording and playback modes. In general, a second motor is provided to selectively drive the take-up reel in a fast-forward mode or to selectively drive a supply reel in a rewind mode. Suitable transmission couplings are provided so that only one of the supply and take-up reels is driven; and when the take-up reel is driven, these couplings mutually exclusively determine the speed. In a typical device, the capstan motor usually is continually energized, and the transmission coupling selectively applies this continuous rotary drive to the take-up reel. Heretofore, it has been necessary to rely upon brake shoes for braking both the supply and take-up reels when this rotary drive is removed. Also, in such devices, when the rewind/fast-forward motor is coupled to, for example, the supply reel, brake shoes must be used to brake the freewheeling take-up reel. Conversely, if the high speed motor is coupled to drive the take-up reel, brake shoes must be provided to brake the freewheeling supply reel.
Although such brake shoes heretofore have satisfactorily accomplished their intended purpose, it has been found that suitable control apparatus must be provided for selectively controlling these brake shoes. Typically, such control apparatus includes one or more solenoids to selectively energize the respective brake shoes into an operative braking condition, or a mechanical linkage. Solenoids or linkages require adequate power for their proper operation; and add to the bulk, complexity and cost of the web transport system and, thus, the recording/playback device. However, it has been thought heretofore that the respective rotary members cannot be effectively braked without brake shoes unless these members are driven by fixed gear assemblies. In general, such gear assemblies are not used because they require very high tolerances, and often cannot withstand the abrupt starting and stopping operations which attend the operation of web transport systems as used in recording/playback devices.